WO2011073014A1 - Device and method for diagnosing the connection of a display screen - Google Patents

Abstract

The invention relates to an electronic device (10) including a liquid crystal display screen (14) and a control card (16), the electric tracks (22, 26) of the card (16) and the screen (14) being connected by means of a connector (28), the control card (16) comprising a microcontroller (24) capable of applying electric voltage to at least one connection pad (30), with a view to displaying a given piece of information on the screen (14), characterized in that the control card (16) comprises a diagnostic device (36) which is provided for generating a voltage pulse (V1) on connection pads (30) and for measuring the resulting electric voltage (V2), with a view to determining the status of the connection between the screen (14) and the card (16), on the basis of the value of the measured electric voltage (V2).

Description

 Device and method for diagnosing the connection of a display screen TECHNICAL FIELD

 The present invention relates to an electronic device provided with a liquid crystal display screen in particular intended to be installed on a structural element of a motor vehicle. The present invention also relates to a method for diagnosing the state of connection of the display screen.

BACKGROUND OF THE INVENTION

 In the automotive field, it is common to equip a vehicle with an electronic device comprising two electronic components interconnected by a flexible connector. Such a device is for example an information display device which is intended to be installed on a structural element of the vehicle, such as a dashboard, a console or the like. This device is for example provided for delivering to a user of the vehicle information, such as general information, such as date, time, temperature outside the vehicle or the like. This device is also capable of providing the user with particular information relating to the operation of the vehicle, or even information relating to the operation of an installation equipping the latter, such as a ventilation, heating and / or air conditioning installation.

 When the electronic device is a display device, it generally comprises a first electronic component which is constituted by a liquid crystal display screen and a second electronic component which is constituted by a control card for the implementation of the 'display screen. The control card and the display screen are housed in a housing being arranged for example in superposition of one another. A light source, such as a light-emitting diode or the like, is placed between the display screen and the control board to illuminate the backlight display screen.

 The display screen has a plurality of electrical tracks that include on-screen display segments. Each segment is made of liquid crystals, for example from a method of

photolithography, and is controlled by two electrodes. A voltage is which can be applied to the electrodes of a segment to orient the liquid crystal of the latter so that the light emitted by the light source passes through it. The application of the electrical voltage to a particular segment is controlled by a microprocessor mounted on the control board or by another electronic component of the "driver" type of LCD screen.

 Of course, the screen may also include pixels instead of segments.

 To electrically connect the electric tracks forming the electrodes of the display screen with the electrical tracks connected to the

microprocessor of the control board it is necessary to arrange an electrical connector between the two components.

 In this type of application, the connector used is generally a flexible connector Zebra type which comprises a plurality of conductive carbon lamellae separated by insulating lamellae made of an electrically insulating polymer such as a silicone or the like. The flexible connector is mounted slightly compressed between the control board and the display screen so that the conductive strips are in electrical contact on one side with connection pads of the control board and the other with connection pads of the screen.

 When assembling the electronic device, it happens that the flexible connector is incorrectly mounted so that some connection pads of the screen are not electrically connected to the control card which causes a malfunction of the screen. It also happens that the connector and / or screen is forgotten during assembly which prevents any operation of the electronic device. This type of editing error occurs all the more easily as these editing operations are usually done manually.

It is known to use on the assembly line visual detection systems requiring cameras to detect the presence of components and / or positioning errors. However, these detection systems are particularly expensive to implement and they do not detect all mounting errors. In addition, these systems do not make it possible to detect mounting errors after the electronic device has been installed in complete equipment, for example in the control panel of a ventilation and heating system.

 For example, in some cases, the screen is not mounted on the control card but it is mounted at the very end of assembly, when we come to position the control member, equipped with the screen, on the dashboard of the vehicle carrying the command card. In this case, the diagnosis of the mounting of the electronic device can only be done at the end of the assembly, which notably excludes the use of detection cameras.

SUMMARY OF THE INVENTION

 To solve the problems mentioned above, the invention proposes an electronic device comprising a liquid crystal display screen and a control card for the implementation of the screen, the electrical tracks of the card being electrically connected to the electrical tracks. of the screen via a connector which is in contact on one side with a first series of connection pads carried by the card and the other with a second series of connection pads carried by the screen , the control card comprising an electronic control unit capable of applying an electric voltage to at least one connection pad of the first series in order to display a given piece of information on the screen, characterized in that the control card includes a diagnostic device which is provided to generate a voltage pulse on connection pads of the first series and to measure the electrical voltage resulting in order to determine the state of the connection between the screen and the card according to the value of the measured voltage.

 The term "diagnosis of the state of the connection" here refers to the determination of an operational electrical connection between the control card and the screen following a correct positioning of the connector with respect to the card and the screen. This diagnostic method also makes it possible to detect the absence of the screen and / or the connector.

An advantage of the present invention is that it does not require any modification of the connector, the control board, or the screen and that it does not require a complex external control device. In addition, the present invention can be implemented at any time after the assembly of the screen on the control card.

 According to other advantageous features of the invention:

 the diagnostic device comprises an electronic control unit which is arranged on the control card;

 the electronic control unit is constituted by the microcontroller which controls the screen;

 - the connector is a flexible connector;

 the flexible connector comprises an alternating succession of electrically conductive lamellae and electrically insulating lamellae oriented parallel to the lateral edges of the flexible connector so that the ends of a conductive lamella and the ends of an insulating lamella are arranged alternately along longitudinal edges of the flexible connector;

 the electrically insulating lamellae are made of a flexible plastic material, in particular silicone.

 The invention also proposes an interior equipment of a motor vehicle comprising at least one control member provided for controlling an operating parameter of the equipment, characterized in that an electronic device according to one of the preceding characteristics is arranged in the controller so that the display shows information related to the operating parameter of the equipment. This equipment belongs for example to a ventilation system, heating and / or air conditioning.

 The invention also proposes a diagnostic method for an electronic device according to one of the preceding characteristics, said method being intended to determine the state of connection of the screen with the control card. It is characterized in that it comprises the following steps:

 generating a voltage pulse on at least one connection pad of the first series,

 measuring the electrical voltage on one or more associated connection pads of the first series,

 comparing the measured voltage with a threshold value,

- transmission of a diagnostic signal representative of the state of the connection, said diagnostic signal being positive when the measured voltage is greater than the threshold value and negative when the measured voltage is lower than the threshold value.

 The method is preferably implemented by means of an electronic control unit which is arranged on the control board. The electronic control unit is constituted by the microcontroller which controls the screen.

BRIEF DESCRIPTION OF THE DRAWINGS

 Other features, objects and advantages of the invention will appear on reading the detailed description which follows, and with reference to the accompanying drawings, given by way of non-limiting example and in which:

 FIG. 1 is an exploded perspective view which represents

schematically a control panel equipped with a display device made according to the teachings of the invention;

 FIG. 2 is a diagram illustrating the electrical connection between the control card and the screen of the display device of FIG. 1;

 FIG. 3 is a diagram which illustrates the electrical supply circuit of a segment of the display screen of FIG. 2;

 Fig. 4 is a diagram showing the supply voltage versus time and showing a voltage pulse used to diagnose the state of the connection of the display device of Fig. 1;

 FIGS. 5 and 6 are diagrams similar to that of FIG. 4 which represent in parallel the voltage pulse and the resulting voltage measured by the microcontroller fitted to the display device of FIG. 1. DESCRIPTION OF THE PREFERRED EMBODIMENTS

 In Figure 1, there is shown an electronic device 10 according to a preferred embodiment of the invention. According to this embodiment, the electronic device 10 is a display device which is arranged in a motor vehicle interior equipment 12, in particular in a control panel 12 belonging to a ventilation, heating and / or air conditioning installation. . More particularly, the display device 10 is associated with a rotary control member 13 for controlling a parameter of

operation of the installation such as the interior temperature of the vehicle. The display device 10 comprises a liquid crystal display screen 14 and a control card 16 for the implementation of the screen 14. According to the embodiment shown, the screen 14 is mounted inside. a fixed portion 18 of the rotary control member to be visible to a user through a window 20 adapted.

 The control card 16 is mounted here on a fixed support inside the control panel 12. It comprises electrical tracks 22 shown diagrammatically in FIG. 2, which are provided for electrically connecting a microcontroller 24 carried by the card 16 to electrical tracks 26 of the screen 14. The card 16 generally comprises a light source such as a light-emitting diode 27 provided for backlighting the screen 14.

 The electrical connection between the control card 16 and the screen 14 is made by means of a connector 28 which is in contact on one side with a first series SI of connection pads 30 carried by the card 16 and the another with a second series S2 of connection pads 32 carried by the screen 14. The microcontroller 24 is provided for applying a determined voltage on at least one connection pad 30 of the first series S1 in order to display a given piece of information on the screen 14.

 The connector 28 is preferably a flexible connector. Here is meant by "flexible connector" a connector 28 which can be compressed in the direction of connection without being damaged. Such a connector 28 is known as a laminated elastomeric connector (called "Zebra connector") comprising an alternating succession of electrically conductive lamellae, for example made of carbon, and electrically insulating lamellae, for example made of a plastic material such as silicone. This succession of slats oriented parallel to the lateral edges of the connector 28 forms on the edges

longitudinal members of the connector 28 two opposite connection surfaces which are provided to cooperate respectively with the two series SI, S2 of connection pads 30, 32.

 When assembling the constituent elements of the display device

10, the flexible connector 28 is interposed between the display screen 14 and the control card 16, so that the longitudinal edges of the flexible connector 28 are kept in contact, and finally compressed, respectively against the connection pads 30 of the control board 16 and the connection pads 32 of the screen 14.

 The display screen 14 includes a plurality of electrical tracks 26 each having at least one display segment 34 made of liquid crystals. Each electrical track 26 comprises a connection pad 32 formed at the peripheral edge of the display screen 14. Each connection pad 32 of the display screen 14 is in contact with a first end of a conductive strip of the connector flexible 28, the second end of each conductive strip being in contact with an associated connection pad 30 on the control card 16.

 The microcontroller 24 is able to deliver a voltage to the electrodes bordering each display segment 34 to orient the liquid crystals of the latter so that they let in the light emitted by the light source 27. This voltage is transmitted from the microcontroller 24 to a particular display segment 34 via the corresponding connection pad 30 of the control card 16, then the conductive strip assigned to this connection pad 30, then via the connection pad 32 corresponding to the display screen 14 which is in relation with the electrical track 26 comprising said particular segment 34.

 To control the ignition of a segment 34, the microcontroller 24 applies a determined control voltage between a first connection pad 30 of the card 16 corresponding to a common signal COM and a second connection pad 30 corresponding to a segment signal SEG.

 As illustrated by the diagram of FIG. 3, the electrical supply circuit controlling a display segment 34 of the screen 14 corresponds to a capacitive circuit, the behavior of a segment 34 being electrically equivalent to a capacitor. The conductive lamellae of the connector 28 are electrically equivalent to resistors.

According to the teachings of the invention, the control card 16 comprises a diagnostic device 36 which is provided to generate a voltage pulse VI on each connection pad 30 of the first series SI corresponding to a common signal COM and to measure the electric tension resultant V2 on each associated connection pad 30 of the first series SI corresponding to the segment signal SEG.

 FIG. 4 represents such a voltage pulse V1 applied on a connection pad 30 for a determined duration Tp over a period of time T. The voltage V1 is the output voltage of the control card 16 as an on-off output.

 FIGS. 5 and 6 show an example of pulse VI during a determined duration Tp and the measured voltage V2 by the microcontroller during this period Tp. It is found that the measured voltage V2 is substantially equal to the applied voltage VI, despite a slight loss of voltage over time. The measured voltage V2 remains greater than a threshold value Vs, which indicates a sufficient quality of the connection between the connection pads 30 of the first series SI and the connection pads 32 of the second series S2, for the segment 34 diagnosed. .

 The threshold voltage Vs is here equal to the reading threshold of the control card 16 in all or nothing mode. This reading is done a few microseconds after sending the voltage pulse VI.

 The same pulse VI is applied to each connection pad 30 of the first series S 1 corresponding to a common signal COM so that the entire connection made by the connector 28 can be tested and diagnosed. If at least one measured voltage V2 is lower than the threshold value Vs, the diagnostic device 36 deduces a connection problem at the connector 28. Such a problem is generally due to a misplacement of the connector 28. If all measured voltages V2 are lower than the threshold value Vs, it is possible that the connector 28 or the screen 14 have been omitted altogether during the assembly of the display device 10, which will be detected by the diagnostic device 36 .

 The diagnosis of the display device 10 described above is preferably carried out according to the following diagnostic method.

After mounting the screen 14 in the control member 13, the control member 13 is mounted on the control panel 12 so that the screen 14 comes to connect to the control board 16 by means of the flexible connector 28 or another type of connector. The microcontroller 24 then generates a voltage pulse VI on at least one connection pad 30 of the first series S1, preferably on all the connection pads 30 corresponding to the common signals COM. The resulting electrical voltage V2 on the corresponding connection pads 30 of the first series S1, here the connection pads 30 corresponding to the segment signals SEG, is measured by the microcontroller 24.

 The microcontroller 24 compares the measured voltages V2 with the threshold value Vs. Depending on the result of the comparison, the microcontroller 24 produces positive or negative diagnostic information giving an indication of the state of the connection between the control card 16. and the screen 14.

 When at least one measured voltage V2 is lower than the threshold value Vs, the microcontroller 24 emits a negative diagnostic signal that can be read by a control device (not shown).

 Advantageously, the diagnostic method is implemented during the initialization phase of the display device 10, just after its assembly on the control panel 12. It can also be implemented periodically by the microcontroller 24 and / or on request, for example during a diagnostic phase of the electrical equipment of the vehicle equipped with the control panel 12.

 According to an alternative embodiment, the diagnosis can be made by applying several successive voltage pulses.

 According to another variant embodiment, a diagnostic strategy can be implemented, for example by adapting the frequency or the value of the voltage pulses, so as to enable more precise detection of the origin of a possible connection fault.

Claims

An electronic device (10) comprising a liquid crystal display screen (14), a flexible connector (28), and a control card (16) for implementing the screen (14), the tracks electrodes (22) of the board (16) being electrically connected to the electrical tracks (26) of the screen (14) by via the flexible connector (28) which is in contact on one side with a first series (SI) of connection pads (30) carried by the card (16) and on the other with a second series (S2) of connection pads (32) carried by the screen (14), the control card (16) comprising an electronic control unit (24) capable of applying an electric voltage to at least one connection pad (30) of the first series (SI) for displaying information given on the screen (14),  characterized in that the control board (16) comprises a diagnostic device (36) which is arranged to generate a voltage pulse (VI) on connection pads (30) of the first series (SI) and to measure the resulting voltage (V2) to determine the state of the connection between the screen (14) and the board (16) as a function of the measured voltage value (V2). 2. Electronic device (10) according to the preceding claim, characterized in that the diagnostic device (36) comprises an electronic control unit (24) which is arranged on the control card (16). 3. Electronic device (10) according to the preceding claim, characterized in that the electronic control unit (24) is constituted by the microcontroller which controls the screen (14). 4 Electronic device (10) according to any one of the preceding claims, characterized in that the flexible connector (28) comprises an alternating succession of electrically conductive lamellae and electrically insulating lamellae, oriented parallel to the lateral edges of the flexible connector (28) so that the ends of a conductive lamella and the ends of an insulating lamella are arranged alternately along the edges longitudinals of the flexible connector (28). 5. Electronic device (10) according to the preceding claim, characterized in that the electrically insulating lamellae are made of a flexible plastic material, in particular silicone. 6. Interior equipment of a motor vehicle (12) comprising at least one control member (13) provided for controlling a parameter of operation of the equipment (12), characterized in that an electronic device (10) according to any one of the preceding claims is arranged in the control member (13) so that the screen (14) displays a information related to the operating parameter of the equipment (12). 7. Interior equipment of a motor vehicle (12) according to the preceding claim, characterized in that it belongs to a ventilation system, heating and / or air conditioning. The diagnostic method for an electronic device (10) according to any one of claims 1 to 5, said method for determining the state of connection of the screen (14) with the control card (16), characterized in that it comprises the following steps:  generating a voltage pulse (VI) on at least one connection pad (30) of the first series (SI) corresponding to a common signal (COM),  measuring the electrical voltage (V2) on one or more associated connection pads of the first series (SI) corresponding to a segment signal (SEG), - comparing the measured voltage (V2) with a threshold value (Vs), - transmitting a diagnostic signal representative of the state of the connection, said diagnostic signal being positive when the measured voltage (V2) is greater than to the threshold value (Vs) and negative when the measured voltage (V2) is lower than the threshold value (Vs). 9. Method according to claim 8, characterized in that it is implemented by means of an electronic control unit (24) which is arranged on the control card (16). 10. Method according to claim 9, characterized in that the electronic control unit (24) is constituted by the microcontroller which controls the screen (14).